1. Field of the Invention
The present invention relates to signature verification devices, and more particularly, to a writing stylus that is sensitive to writing pressure.
2. Description of the Prior Art
Personal identification systems are needed in situations where one must authenticate his identity as a pre-condition to taking certain actions or receiving certain privileges. Practical examples of the need for personal identification include limiting access to classified information or militarily secure areas, honoring bank checks or other forms of commercial paper, and extending credit in a credit card transaction. In each of these instances, the importance of making an accurate determination of an individual's identity is proportioned to the security and financial risk of misidentifying him or her.
The prior art contains various devices that adjudge an individual's identity on the basis of a unique identifying characteristic associated with the individual. These identifying characteristics include finger prints, lip prints, voice graphs, and handwritten signatures. Personal identification devices using these characteristics have various degrees of reliability and practicability.
Verifying an individual's identity through the comparison of his or her handwritten signature sample against a reference signature is one of the most practicable and reliable methods. Various indicia or characteristics associated with the individual's signature or act of signing can be measured to discriminate between genuine and forged signatures. Included among those indicia or characteristics are pen velocity, pen direction, and pen pressure.
Focusing on the use of pen pressure, the pressure may be sensed either in the writing instrument or on the writing surface. The difficulty of the latter approach, i.e. using the writing surface, is in the inflexibility of requiring that the signature occur at the fixed situs of the surface. Moreover, it would be expensive to provide pressure sensitive surfaces in all the instances where they are needed, e.g., every teller's window in a bank using signature verification would have to be provided with a pressure sensitive platen.
For broad applicability, the preferred approach is to use the pen or other type of writing stylus as the pressure sensing member. However, for the pen to be practicable it must meet several important design considerations, including high sensitivity to loading pressure, ruggedness in reliability for use in a commercial or retail environment, refillability to allow the ink supply to be replenished, and ease of manufacture to make the cost competitive with other forms of personal identification device.
These foregoing considerations define the primary objectives of the present invention.